"In this test, we'll be extending Facebook's rich targeting to improve the relevancy of the ads people see, provide even greater reach for Facebook advertisers, and help developers better monetize their apps."

Instead of using an outside ad-serving platform, the social media giant is collaborating directly with a handful of advertisers and publishers, Krishnan added, but didn't name the partners.

The trial is aimed at helping developers monetize apps more quickly amid the popularity of free apps, which don't always return a developer's investment. It could also help make ads on mobile devices more relevant.

The move is a challenge to Google's AdSense, a long-established platform that serves up automatic text, image, or video ads to targeted websites. AdSense has delivered nearly 30 percent of Google's revenue in recent years.

Facebook has long been planning and experimenting with mobile ads apart from those on its own Facebook mobile platform, but it said the current trial is different from previous forays because of the direct partnerships with advertisers and publishers. The current test is more like a mobile ad network, Krishnan said.

In the third quarter of 2013, Facebook's mobile ads made up 49 percent of its US$1.8 billion advertising revenue, up 66 percent from the same quarter in the previous year.

Join the Network World communities on Facebook and LinkedIn to comment on topics that are top of mind.